Non-aqueous organic solvents which are used to dissolve molecules containing a functional group, which react with a hydrophilic group at one end (hereinafter referred to as surface active material), are prepared by refining commercially available solvents and preserved with added drying agents. Those solvents which have been preserved should be refined before use. Further, when the surface active material is dissolved in the solvent, the drying agent is removed.
In a further aspect, while a monomolecular film is formed on a substrate containing hydrophilic groups at the surface with a dehydrohalogen (i.e., hydrochloric acid) removal reaction (dehydrohalogenation reaction) brought about by dipping the substrate in a non-aqueous organic solvent with a surface active material dissolved therein. In such a case no catalyst for promoting the reaction is added.
The principle of production of a chemically adsorbed monomolecular film is to form a monomolecular film by utilizing a dehydrohalogenation reaction between hydroxyl or like hydrophilic groups at a substrate surface and chlorosilyl or like functional groups at one end of a surface active material.
Therefore, if water molecules are present in the non-aqueous organic solvent with the surface active material dissolved therein, they react with the surface active material which results in gel polymerization of the surface active material, thereby causing inadequate monomolecular film formation. Further, in the prior art method of forming a chemically adsorbed monomolecular film, a molecular sieve or like drying agent is added to refine the non-aqueous organic solvent and removed right before dissolving the surface active material. Therefore, it is important to prevent the drying agent from being introduced into the solvent.
In a further aspect, in forming the monomolecular film, halohydrogen is generated in the solvent. It has been thought that halohydrogen is only slightly generated compared to the amount of the solvent and surface active material and that it does not substantially affect the reaction. However, it is thought to be generated on the substrate surface and thus partly increase its concentration at the substrate surface. Actually, in the last stage of the monomolecular film formation, the rate of formation is considerably reduced, and a long time is required until formation of the monomolecular film is complete.
An object of the invention is to provide a method, which can prevent halohydrogen concentration increase during film formation accompanying a halohydrogen removal reaction and permits simplification of operation. This would permit a chemically adsorbed monomolecular film to be efficiently obtained in a short period of time and give a solution to the prior art problem.